TanishqVyas
April 5, 2023
298 views
0 votes
2 Answers

Scenario

I have the following type of function that I wish to test. This function has

File to be tested

export const doSomething = () => {

    sequelize.transaction(async t => {
        customModel.upsert(dataObject, { transaction : t })
        
        otherCustomModel.upsert(otherDataObject, { transaction : t })
    })
    
}

Here customModel and otherCustomModel are valid models written using sequelize.define in their respective files.

Here sequelize is the following thing

import Sequelize from 'sequelize';

const connectionParams = {
// assume valid config is present
}

const sequelize = new Sequelize(connectionParams);

(async () => {
    try {
        await sequelize.authenticate();
        console.log('Sequelize authenticated successfully');
    } catch (error) {
        console.log(`Unable to connect to the database: ${error}`);
    }
})();

export default sequelize;

Requirements

I wish to write a testcase with the following checks:

Test that the following functions are called once.
- transaction
- customModel.upsert
- otherCustomModel.upsert
The entire function executes

How can I go ahead and mock a sequelize transaction using jest for such functions?

My Test

test("text", () => {
    
    // mocks
    sequelize.transaction = jest.fn()
    customModel.upsert = jest.fn()
    otherCustomModel.upsert = jest.fn()
 

    doSomething()

    // assertions
    expect(sequelize.transaction).toBeCalled();
    expect(customModel.upsert).toBeCalled();
    expect(otherCustomModel.upsert).toBeCalled();

})

Error Faced

expect(jest.fn()).toBeCalled()

    Expected number of calls: >= 1
    Received number of calls:    0

62 |        expect(sequelize.transaction).toBeCalled();

Versions

S No.	Dependency	Version
1	sequelize	^6.19.1
2	jest	^27.5.1

P.S. : Any other suggestions to enhance my test case are welcomed!

Answers

You should be able to do it e.g. like this:

const sequelize = require('sequelize');
const customModel = require('<your module>');
const otherCustomModel = require('<your module>');

jest.mock('sequelize', () => ({
    transaction: jest.fn(() => jest.fn()),
}));
jest.spyOn(customModel, 'upsert');
jest.spyOn(otherCustomModel, 'upsert');

And in you test case:

sequelize.transaction.mockImplementation(() => jest.fn());
otherCustomModel.upsert.mockImplementation(() => jest.fn());
customModel.upsert.mockImplementation(() => jest.fn());

and after that you can do your assertions e.g.:

expect(sequelize.transaction).toBeCalled();

I would write it something like this

describe('doSomething', () => {
  beforeAll(() => {
    doSomething()
  })

  it('should call transaction with a callback', () => {
    expect(sequalize.transaction).toHaveBeenCalledWith(
      expect.any(Function)
    )
  })

  describe('the transaction', () => {
    let mockTransaction = { prop: 'dummy transaction object' }
    
    beforeAll(() => {
      const transactionCallback = sequalize.transaction.mock.calls[0][0]
      transactionCallback(mockTransaction)
      // presuming you're NOT using jest.spyOn on sequalize.transaction
      // you have to call the callback passed to it
    })

    it('should have called customModel.upsert', () => {
      const dataObject = expect.objectContaining({
        // ...expected properties
      })
      expect(customModel.upsert).toHaveBeenCalledWith(
        dataObject, { transaction : mockTransaction }
      );
    })

    it.todo('should have called otherCustomModel.upsert ... same as above')
  })
})

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How to mock a sequelize transaction with jest – Javascript